Wednesday, April 12, 2017

When black hole remnant nonsense is sold as science

One of the things I simply couldn't stand – and still cannot stand – about the university environment was its complete inability to do something about 100% self-evident fraudsters that live as parasites on the system. Competent people want to be "nice" which means that much of the environment is controlled by filth like Lee Smolin that has nothing whatever to do with the professional science.

Genius: Off-topic, there is a new cool 2-minute excerpt from Genius showing how Einstein met Mileva Marić, his first wife, after she trumped him in a physics exam and some ancient Greek physical philosophy. ;-)

In early 2009, Smolin and another crackpot often mentioned on this blog wrote a paper promoting hippie non-solutions to the black hole information paradox which they laughably called "conservative solutions". More or less every aspect of that paper was completely wrong and ludicrously wrong – Smolin's co-author recently admitted (bragged, I would say) that she realizes that every paper she has ever written on quantum gravity has been worthless garbage but she wrote them, anyway, because she was able to actually get money for this garbage.

I think that fraudulent scumbags like that should be spending years in prison or minutes on a rope. The reality is different: actual physicists can't even shout at this scum. In fact, they are even afraid of publishing their name while overly politely criticizing them, as we will see momentarily.

Two days ago, at the notorious website of his fellow crackpot Peter Woit, Smolin tried to defend the indefensible – his hippie paper with Hossenfelder and the black hole remnants.

In his first comment, Smolin just superficially reiterates that theirs is a "conservative solution" and refers to the would-be authorities like Rovelli and Ashtekar. He also mentions that the black hole interior is a "bag of gold", a big volume of space, as Smolin puts it. But the "bag of gold" is irrelevant for this whole discussion about remnants – because the black hole exterior is completely sufficient to see why they can't work – and Smolin even describes the meaning of the "bag of gold" totally incorrectly.

At any rate, again, phrases such as the "bag of gold" have nothing to do with the reasons why the black hole remnants can't exist. Some of the actual reasons were summarized by a commenter nicknamed "Reader" – obviously a professional researcher in the black hole information industry. As I already mentioned, it's no coincidence that the people who actually have a clue are hiding their names – they must believe that they must be doing so. It's pathetic. He or she wrote:

Lee, this proposal has features that make it seem not so conservative after all. As is well known, if the thermality of the radiation only breaks down once the black hole becomes of Planckian mass, then the remaining object must decay over a very long timescale for its radiation to purify the full state. Indeed this timescale can be made arbitrarily long by increasing the mass of the original black hole. So this scenario requires very long lived remnants. More seriously perhaps, it seems impossible to make this work for a black hole formed in AdS. Putting aside anything to do with AdS/CFT, AdS acts like a finite sized box, so a state of radiation of total energy \(M_{\rm Pl}\) has a small maximum entropy. In this case there is no way for a Planckian remnant to decay into a gas of (arbitrarily) high entropy quanta whose state would purify that of the Hawking radiation emitted earlier. So while it is logically possible for black holes to release their information in Hawking radiation in asymptotically flat space (while only modifying Planck scale physics) this seems impossible in AdS. I find that highly problematic.

OK, what did "Reader" say? If the evolution is unitary but the black hole evaporation is exactly thermal as long as the black hole is significantly greater than a length scale comparable to the Planck length, then the final decay products of the remnant must carry the whole information. In a truly infinite spacetime such as the Minkowski space, the huge information from the initial "solar size" black hole, to pick an example, may be encoded in the exact directions or timing of the photons coming from the decay of the remnants.

However, the radiation in the AdS space is basically equivalent to that in a box. The AdS space may be visualized as a solid cylinder and massive (and massless) objects are being repelled (or reflected) from the AdS boundary. The fact that there is an infinite proper volume concentrated near the boundary of the AdS (cylinder) doesn't change the fact that the entropy of the radiation emitted at the AdS center behaves just like the radiation in a box. There are just finitely many momentum modes so the radiation cannot carry an arbitrarily high entropy.

OK, the objections by "Reader" are self-evidently valid and serious. Smolin replies to them and claims that they're "fallacious". Does he have arguments? No but he has some dumb caricatures of an argument. Smolin says that "Reader" isn't right that the radiation in AdS has a low entropy because... the black hole contains a "bag of gold" which is big and therefore carries a high entropy. Well, in that case, it's even worse because he clearly violates the second law of thermodynamics. A high-entropy "bag of gold" would have to evaporate into the low-entropy AdS radiation!

Smolin wants to dispute the unquestionable comment that the initial black hole had a high entropy:

Why? To the extent that the overall state is purified, the entropy is low.

What!? Smolin clearly misunderstands the concept of entropy at the very basic level. Undergraduate students should fail their statistical physics course if they misunderstand it in this way. Smolin basically believes, like many confused students, that the entropy is \[

S = -{\rm Tr}(\rho \ln \rho)

\] and because you may always assume that the density matrix \(\rho\) is pure, \(\rho=\ket\psi \bra \psi\), the entropy ends up being zero, \(S=0\). But that's not what we mean by an entropy of an object. To calculate the entropy, you have to substitute \(\rho\) that has comparable probabilities for all macroscopically indistinguishable states from the state you are discussing. So whether you like it or not, the entropy of an object is always\[

S \sim \ln N

\] where \(N\) is the number of macroscopically indistinguishable states from the given one. If the entropy could be said to be always zero because it's always in principle possible to assume that the state is pure, then the concept of entropy – and the whole statistical physics and thermodynamics – would be totally meaningless, vacuous, worthless, and null. Crackpot Smolin obviously seems to believe that these disciplines of physics are meaningless, vacuous, worthless, and null – as meaningless, vacuous, worthless, and null as his research or himself personally.

In the last incoherent paragraphs of the comment, we see the name of Rovelli while Max Planck is spelled as "Plank". The sentences are isolated from each other and each of them is absolute rubbish. For example, one of the last ones is

There is no singularity and this means no information is lost, whatever the fate of the region containing it.

But all propositions above are self-evidently wrong. The formation of a singularity cannot be prevented as long as gravity works at least approximately at least at long distances, as the singularity theorems guarantee. And even if something were qualitatively changed about the singularities, it would have no impact whatever on the information loss paradox because the information loss paradox is seen from outside – it only arises when the interior fully disappears – so this paradox doesn't even have to assume that anything inside the black hole event horizon exists!

It's very obvious that just like his fellow crackpot and co-author Sabine Hossenfelder (and a big fraction of the laymen, as I learned during many popular talks I gave), Smolin believes that the "key feature" of a black hole – and the reason why the information loss problem arises at all and seems hard – is the singularity. But this is a complete delusion. The defining feature of a black hole – and the first locus which produces the black hole information problem – is the event horizon, not the singularity! This statement is really elementary. Every competent physicist knows it. The black hole is a hole because once you fall behind the event horizon, you can't get back – so it is the event horizon that makes it a "hole". The event horizon also makes it black because not even light may escape from the points beneath the horizon. And the same event horizon is also the root of the information loss paradox because the information cannot escape from beneath the horizon. In all these questions, it's the event horizon where the novelties and potential hurdles arise. The singularity is just an irrelevant place where the life of an observer ends. When you modify some events near the singularity, it's too late for solving anything that matters.

Every damn statement that Smolin makes is wrong – often at a very elementary level – and everything he says to be relevant for the problem is self-evidently irrelevant, anyway. And vice versa. He just denies and overlooks everything that is relevant.

"Reader" tries to respond to Smolin again and more slowly. He explains that the radiation from a tiny, Planckian object cannot have the required huge entropy. Also, one must decide whether the interior of the remnant is accessible from outside in principle or not. If it is not accessible even in principle, then the information is really lost. If it is accessible, then the precise identity of the remnant represents new degrees of freedom and one predicts the infinite pair production, among other things.

Also, "Reader" denounces Ashtekar's comments as incomprehensible while Rovelli's comments assume a big deviation from GR even when the curvature invariants are low – which generically predicts a contradiction with the successful tests of general relativity, a contradiction that has to be addressed and contained for the theory to be taken seriously. At the end, he also mentions that AdS/CFT says a clear "No" about remnants. Small objects in the AdS space may be fully classified by the CFT and there are simply no states that could be identified with the remnants.

You could in principle argue that in the flat space, the rules of quantum gravity are different than they are in the AdS space. But it's really implausible. The low-curvature AdS space behaves just like the flat space if the laws of locality are preserved. It sounds extremely unconvincing that quantum gravity is made consistent in two or several completely and qualitatively different ways. Moreover, one may also discuss the flat space using Matrix theory which says the same thing about the remnants as the AdS/CFT correspondence: They just don't exist.

But because the second side is Lee Smolin, these exchanges are completely meaningless because Smolin not only denies AdS/CFT or any important tool that is used to analyze the general questions by the actual physicists. He also denies elementary concepts such as the entropy and its basic properties such as its being nonzero and increasing.

Clearly, Smolin's words aren't addressed to actual physicists. They are addressed to completely ignorant laymen who are "capable" of buying that Smolin is as competent as other physicists if not more so. And he must surely be even better – because he is a far left whacko which is what his target audience likes about a scientist or anybody. And this complete fraud can get away with it. What sort of human beings are you, the folks in Waterloo, if you allow your institute to deceive the whole public in this way literally for decades if not lifetimes? All of you know that what Smolin is doing is a big scam – just like Andrea Rossi's cold fusion etc. – but you must find it convenient to indirectly collaborate with him.